July 21, 2011 9:22:46 AM PDT

We encounter billions of germs every day through the air we breathe, the food we eat and the things we touch. Considering all of the potential threats to your body, including viruses, bacteria, fungi, toxins, and parasites, it's amazing that most of them have little or no impact on your health and well-being. We enjoy relative safety from these threats thanks to the complex arsenal of defenses that make up the human immune system.

You can get a sense of how much the immune system does for you by reflecting on what happens when it stops working. For example, the reason the HIV virus is so dangerous is because it destroys immune cells and stops the immune system from responding to new infections. HIV patients are likely to have repeated sinus, lung and gastrointestinal infections. Also, patients undergoing chemotherapy often have low white blood cell counts, and must take extreme care not to get bacterial infections of any kind. When the immune system is not working, even the most common infection can be lethal.

Given all of the work that it does to protect the body from various attackers, it would be an understatement to say that the immune system is complex. There are many organs involved, several distinct systems working together, millions of different types of immune related cells playing a role, and countless paths for communication and coordination traveled throughout the process. The immune system is fascinating not only because of how each of these parts works, but also because of the complex integration and control required to keep this crucial system in balance.

For more information about the immune system and how it works, refer to this publication titled "The Immune System" from the US Department of Health and Human Services: http://www.niaid.nih.gov/Publications/immune/the_immune_system.pfd

Control and Balance

The key to the power of the immune system lies in its control. For this reason, how invaders are recognized and how defenses are started and stopped are topics of much research. You can have the best defenses in the world, but if they cannot be controlled and executed properly, they are useless or even harmful. An immune system working effectively, in balance, and in control is critical to your overall health.

To explain the control of the immune system, mediacal professionals describe the "Th1/Th2 balance". Think of your immune systema as a seesaw, and imagine Th1 on one side and Th2 on the other. The Th1 side controls the response that fights threats that happen inside cells, while the Th2 side controls te response to threats that occur outside the cells. A healthy immune system is balanced and dynamic, switching back and forth between Th1 and Th2-triggered activity depending on the threats at hand. This balance allowsfor quick action to eliminate a threat, and then a swift return to neutral, so that the system is ready to respond appropiately to whatever is coming next.

Recent research shows that sometimes the immune system can become unbalanced or stuck, favoring one side or the other of the Th1/Th2 seesaw. The result: an inappropriate dominant Th1 or Th2 response. Dominant Th1 or Th2 responses are directly linked to certain diseases and conditions.

Immune system imbalances can happen as a result of poor nutrition, lack of sleep, physical strain, and emotional stress. Major life events such as moving, getting married, having a baby, or the loss of a loved one sometimes trigger the emotional stress that thrusts the system out of balance, but less dramatic events, like difficult social situations, work, school, money problems, constant travel, and other everyday situations can also be to blame.

In these instances, the immunes system needs helo to regains its balance. Once it's stable, the immune system and its incredible power can work for you, and help to restore a feeling of well-being.